System for determining pneumatic tire pressure for motor vehicle by comparing actual to adequate wheel rotational speed

Abstract

A pneumatic tire pressure determining system on a motor vehicle detects an actual rotational speed difference between rotational speeds of front or rear left and right road wheels of the motor vehicle, detects an operating condition of the motor vehicle, and calculates an adequate rotational speed difference between rotational speeds of the front or rear left and right road wheels based on the detected operating condition of the motor vehicle. The system compares the adequate rotational speed difference and the actual rotational speed difference, and when the difference between the compared actual and adequate rotational speed differences exceeds a predetermined value, the system determines a pneumatic tire pressure reduction.

What is claimed is: 
     
       1. A system for determining a reduction in the pneumatic tire pressure of road wheels on a motor vehicle, comprising: first means for detecting an actual rotational speed difference between rotational speeds of front left and right road wheels of the motor vehicle;   second means for detecting an operating condition of the motor vehicle;   third means for calculating an adequate rotational speed difference between rotational speeds of the front left and right road wheels based on an output signal from said second means; and   fourth means for comparing said adequate rotational speed difference calculated by said third means and said actual rotational speed difference detected by said first means, and determining a pneumatic tire pressure reduction when the difference between the compared actual and adequate rotational speed differences exceeds a predetermined value.   
     
     
       2. A system for determining a reduction in the pneumatic tire pressure of road wheels on a motor vehicle, comprising: first means for detecting an actual rotational speed difference between rotational speeds of rear left and right road wheels of the motor vehicle;   second means for detecting an operating condition of the motor vehicle;   third means for calculating an adequate rotational speed difference between rotational speeds of the rear left and right road wheels based on an output signal from said second means; and   comparing means for comparing said adequate rotational speed difference calculated by said third means and said actual rotational speed difference detected by said first means, and determining a pneumatic tire pressure reduction when the difference between the compared actual and adequate rotational speed differences exceeds a predetermined value.   
     
     
       3. A system according to claim 1 or 2, wherein said operating condition of said second means determined by detecting a lateral acceleration of the motor vehicle and detecting a speed of the motor vehicle. 
     
     
       4. A system for determining a reduction in the pneumatic tire pressure of road wheels on a motor vehicle, comprising: first means for detecting rotational speeds of drive and non-drive road wheels of the motor vehicle and calculating an actual ratio of slippage between the drive and non-drive road wheels based on the detected rotational speeds;   second means for calculating an adequate ratio of slippage of the drive road wheels if the pneumatic tire pressure of the drive and non-drive road wheels is determined as normal from an operating condition of an engine of the motor vehicle; and   comparing means for comparing said actual ratio of slippage calculated by said first means and said adequate ratio of slippage calculated by said second means, and determining a pneumatic tire pressure reduction when the difference between the compared actual and adequate ratios of slippage exceeds a predetermined value.   
     
     
       5. A system according to claim 1, 2, or 4, further comprising means for disabling said comparing means if at least one of the following conditions a, b, c, d, e, f, g is satisfied: a: the motor vehicle is not running;   b: the motor vehicle is braked;   c: the motor vehicle is running on rough terrain;   d: a lateral acceleration of the motor vehicle is not within a predetermined range;   e: a steering angle of the motor vehicle is not in a predetermined range;   f: a longitudinal acceleration of the motor vehicle is not within a predetermined range; and   g: an engine output torque of the motor vehicle is not within a predetermined range.   
     
     
       6. A system according to claim 1, 2, or 4, further comprising means for enabling said comparing means if a lateral acceleration of the motor vehicle falls within a predetermined range, a longitudinal acceleration of the motor vehicle falls within a predetermined range, a steering angle of the motor vehicle falls within a predetermined range, and an engine output torque of the motor vehicle falls within a predetermined range.